1915.] SCHLESINGER— VARIATIONS OF LATITUDE. 357 



its direction; for an unvarying current would merely modify the 

 Eulerian term once for all and would leave the latitude variations 

 otherwise unchanged. A similar suggestion has been made with 

 regard to air currents, and appeal has also been made to unequal 

 deposits of snow and ice on two opposite hemispheres of the earth, 

 to account for the annual term. It seems to me that these explana- 

 tions have not been subjected to the critical numerical tests that are 

 possible and desirable. The meteorological data are doubtless com- 

 petent to enable us to compute at least the order of the effects in 

 the latitude variations that we should expect from these various 

 causes. Furthermore the annual term is probably variable in its 

 amplitude, and it is important to ascertain how (if at all) these 

 changes are related to the corresponding meteorological observa- 

 tions. 



One other term must be mentioned in this brief summary. A 

 few years ago Kimura of Japan made the important discovery (the 

 most striking contribution to astronomy that has ever come out of 

 Asia) that the latitudes of all stations are affected by a variation 

 that does not depend upon the longitude but which is the same for 

 all points in the same latitude. In other words there is present a 

 variation that is not due to the wanderings of the pole. To ascer- 

 tain more closely the nature of this term, the International Geodetic 

 Association extended its latitude service temporarily to the southern 

 hemisphere, with the result that the term was found to be of pre- 

 cisely the kind that would be caused by an annual wandering of 

 the center of gravity of the earth to and fro along the axis of rota- 

 tion. This must be regarded merely as an illustration and not as 

 an explanation, for so great a change (about three meters) in the 

 position of the center of gravity is excluded on other and very con- 

 clusive grounds. No plausible explanation for the Kimura term 

 has as yet made its appearance, and as a consequence the reality of 

 the term has been questioned from every possible point of view. 

 Many explanations have been advanced, each of which sought to 

 account for the term as merely an instrumental effect or the like, 

 just as was the case twenty years earlier with the whole of the lati- 

 tude variation itself. Against such attempts the Kimura term has 



